Improved centring-tool



WILLISTON I. ,ALVORD, OFBRIDGE-POR'I, CONNECTICUT.

Letters Patent No. 96,6543, lated November' 9,1869.

IMPROVE!) CNTRING-TOOL.

The Schedule referred to in these Letters Patent and making part of the same.

' 'o all whom. it may concern Be it known that I, WILms'roN I. ALvoRn, of the city of Bridgeport, in the county of Fairfield, and State of Connecticut, have invented a new'and useful improvement in Centiing-llools or- Instruments; and I do hereby declare that the following is a full, clear, and exact description of the'construction, character, and operation of the same, reference being had to the accompanying drawings, which make palt of this specification, in which Figure 1 is a perspective view of. the tool, showing vall its parts .in their propel' connection.

Figure 2 is a section of'the same, cut longitudinally through one of the jaws, the circle or plate, cylinder, centre, two of the screws, and one of the springs.v

My improvement consists in constructing a tocl or instrument which will point out the exact centre ot' any piece of' cylindrical metal, Src., for turning, drill-` ing, 85e., or if itis, iu its cross-section, an equilateral triangle, a hexagon, enoagon, 85e.

I make the hollow cylinder A of' cast-metal, or any` other suitable material, with the most careful and exact drilling and turning, as indicated in section at A A, tig. 2. so that the hubor nave a, of the circle B, may slide freely, yet steadily, upon the outward surface, and so that the solid centre C may pass through the ealibreof the cylinder with freedom, and yet comparatively air-tight, so as to render its effect incentringpractcally true.

' I make the circle or disk B ot malleable cast-iron, or any other suitable| material, with a suitable lmb or nave, as shown at (t, on which l atlix small springs, as indicated at g g, iig. 1, and through which circle or disk l make nmrtises, as shown at l l, iu which the bars EF G work, all as indicated in iig 1.

1 make the centre C ot' cast-steel, or any other suitable material, of practically a perfectly cylindrical form', as represented at C, lig. 1 and indicated in section in 2, with a central or conical point, l), at one end, and a suitable knob at the other end, to receive a blowfrom a hammer, as shown atl C and C', figs. 1 and 2.

I make the stationary part or frame of the tool ofmalleable cast-iron, or any othel` suitable material, substantially in the form shown `atD, iig. 1, and indicated in section at D D, tig. 2, which, by means of a screw, shown yat C, figs. 'l and 2, liolds or supports the cylinder vin its proper longitudinalposition, and the bars 1'), F, and G, are all connected, as hereinafter described.

l make the bars ot cast-steel, or any other'suitable material, substantially in the form or shape shown at E, F, and G, iig. l, one ot' which bars is Valso shown at lil, tig. 2.

I attach these bars, E, F, and G, to the frame D by means ot' joint-pins, as indicated'at d and e, tig. 1, and d, ligl, or by any other convenient `joints, and to the hub or nave a, I secure or'atx slight springs,

as indicated at g g', to throw the bars outward, in the r n mortises, so as to carry their points h h h" away from the material, to release it; and to regulate the bars E, F, and' G, so.that their points h h' h" may meet at the `exact centre, I tit adjusting-screws in the periphery ot' the circle B, as indicated at c' i', lig; 1, and in sec- .tion in tig, 2, by which I can rectify any defect in the construction ofthe circle B, or the wearing of the points h h 1a.",(the mort-ises in the circle or disl; B 4being long enough for that operation.) v

Haring made the several parts, asbefore described, I pass the rear ends of the bars E, F, and G, through the lnortisesin the circle or disk B, and into theljoint spaces in' the front or main collar of the frame D, as shown atl; le', tig. 1, and indicated at k, ig. 2, where I secure them in their positions by suitable joint-pins, asbefore described. I then pass the cylinder A through the frame D and the nave a, of the circle B, and secure it in the desired position by a bindingscrew, as indicated at c, figs. land 2. I then insert the solid centre, as indicated at C, iigs. 1 and 2, when the tool willl he ready for use.

'To use this tool or centrer, l draw back the centre C until it is ont ot' the way. I-then pass the Vends la. It It" of the. jaws over the article to be centred, until the cylinder A rests on the end of the article, when, by forcing the circle B forward, or in the direction indicated by the dart, the three jaws, E, F, and G, will equally approach the centre until their points, It h h, are stopped by the out-er surface of the article to be centred, andthen by forcing,r down the centre. C, by a hammer or otherwise, the pointb will mark the exact centre ofl the article.

The advantages ot' my improvement consist in that it designates the exact-'centre ot' any article which is', in its cross-section, a circle, an equilateral triangle, a.

hexagon, or any other similar polygon; and any other number ot' jaws can. be used, it' found necessary, as

a'ny mechanic will readily understand.

lVhat I claim as my in\'ention,and desire to secure by Letters Patent, is

` The combination of the frame D, jaws E, F, and G, sliding circle or disk B, cylinder A, and cent-re- C, when they are constructed and arranged substantially as herein described and set forth. WILLISTON I. ALVORD. Witnesses:

P. C. Mo'ULToN,A R. FITZGERALD. 

